AMD HD 6850 compatible with Premier Pro CC?

I've been video editing on a cheap laptop (brand wise)with a first generation i7 and a discrete graphics card. Premiere CC (not 2014 nor 2015) was "okay" but ofc wasn't enough. I built a desktop off of remains which includes Phenom II x4 @ 3.8GHz, 4GB 1600Mhz RAM, 870 chipset mobo, HD 6850 graphics card (not in the adobe supported GPUs list) and MX200 250GB SSD. The problem is that the desktop PC is running slower than the laptop. The green bar goes to red very fast and I get short but frequent freezes in the process. Is a new compatible graphics card going to be the solution and be the best performance upgrade for that system? I just don't wanna spend my last money on a graphics card that won't give enough performance increase. Also, is a cheap but compatible ~$100 graphics card going to be good enough?